1. Field of the Invention
The invention relates to the generation of a random number for use by a central processor of a telephone communication switching system; and more particularly to generating a random number less than a predetermined number produced by the central processor.
2. Description of the Prior Art
The invention was developed for the system shown in U.S. Pat. No. 3,767,863, issued Oct. 23, 1973, by Borbas et al for a Communication Switching System with Modular Organization and Bus, hereinafter referred to as the System S2 patent. The processor for this system is shown in a co-pending application, Central Processor, to Borbas et al, Ser. No. 510,092, filed the same day as this application.
In a common control telephone office, one of the functions performed by the central processor controlling the system is the selection of pieces of equipment to be used on any given call (registers, trunks, links, etc.). In most cases reliability considerations dictate that the initial choice be random. However, because the total number of units in any one set can vary, it is difficult to select a totally random unit if the processor has access to only a random number. To help solve this problem in System S2 it was decided to build a specialized random number generator. In this case the processor would be able to specify a range digit (0 .ltoreq. X .ltoreq. 255) or (0 .ltoreq. X .ltoreq. FF) in hexadecimal notation, prior to the generation of the random number. The traffic distributor receives this range digit and then calculates a random number Y such that 0 .ltoreq. Y &lt; X and returns it to the processor on request.